A motor vehicle storage battery frequently falls into a state of discharge such that it cannot deliver sufficient current to the starter motor. Such discharge state occurs most commonly because of excessive current drain, insufficient charging time, or severe environmental conditions, for example.
To start a vehicle whose storage battery has been partially or completely discharged requires either bypassing the electrical starting system entirely or supplying the electrical starting system with an additional source of external electrical power. The former technique is generally accomplished by push-starting the vehicle and the latter technique by using jumper cables connected to a fully charged external power source in another vehicle. Push starting requires assistance in the form of a push vehicle or human muscle power. Additionally, only cars fitted with standard transmissions can be push started. Jump starting requires the aid of an additional vehicle. Further, cables must be available and must be externally connected, requiring the user to exit the vehicle, and be exposed to the hazards of weather or of a possible battery explosion and associated mishaps as a result of a misconnection of the cables.
Self-contained emergency charging means for charging a vehicle's inoperative battery to enable a vehicle to start have been proposed. For example, U.S. Pat. No. 4,004,208 issued to Tamminen discloses a starting aid which may be contained within a vehicle to provide an emergency power source. The starting aid described therein is not itself readily rechargeable and requires approximately fifteen hours to recharge itself with the vehicle's engine running, because only the additional voltage differential supplied by the vehicle's alternator or generator can be used to recharge the charging aid batteries. Because this voltage differential is very small, no fast charging mode is possible in the starting aid proposed by Tamminen.
U.S. Pat. No. 4,540,929 issued to Binkley also discloses a starting aid unit which is not readily rechargeable and uses a low current regulation system. The unit requires approximately 14 to 16 hours to recharge itself using either vehicle current or an external AC current source. Such long recharging time is needed because the voltage differential between the two battery packs used in the unit and the vehicle voltage source is high enough that the recharging of the battery packs needs to be regulated so as to occur at a much lower voltage in order to avoid overheating or overcharging the battery packs. Accordingly, no fast recharge mode is possible in the unit disclosed by Binkley. Also, due to the size and type of batteries used in the battery packs of the Binkley unit, no fast discharge mode is possible. Moreover, the capability of the Binkley device to recharge a severely discharged vehicle starting battery, i.e., one whose voltage is below 50% of its normal voltage, is highly questionable and seems unlikely.
Other devices proposed in the art include devices disclosed in U.S. Pat. No. 3,504,262 issued to Sada et al. and in U.S. Pat. No. 3,763,415 issued to Ownby. Such devices require either a connection to an external power source, or are insufficiently portable, or require extensive charging and/or recharging times.
Accordingly, it would be desirable to provide a battery charging device which can recharge a discharged storage battery in a relatively short time, e.g., in a minute or less, and whose battery sources are capable of being recharged in a relatively short time, e.g., in a half-hour or less. Such a device should be designed so as to be able to provide sufficient power to recharge in a relatively short time even a severely discharged storage battery, i.e., one whose voltage is below 50% of its rated voltage, as well as a storage battery which has in effect been fully discharged.